1. Field of Invention
Apparatuses and methods consistent with the present invention relate to a display apparatus and a control method thereof, and more particularly, to a display apparatus and a control method thereof that improves adjustment of a color temperature.
2. Description of Related Art
A display apparatus such as a television set can set a color temperature of an image displayed. Specifically, the display apparatus can adjust the color temperature by adjusting a ratio of an image signal's red (R), green (G) and blue (B) brightness. Generally, the color temperature of the display apparatus can be varied in a range between 6,000K and 12,000K.
As illustrated in FIG. 1, a plasma display panel (PDP) television set 10 includes gain adjusting units 11, 12 and 13, an inverse gamma compensating unit 20, an average picture level (APL) adjusting unit 30, a light emitting number determining unit 40, a driving unit 50 and a PDP 60. The gain adjusting units 11, 12 and 13 adjust gains of respective R, G and B channels of an input image signal for application of color temperature. The inverse gamma compensating unit 20 performs an inverse gamma compensation to linearly compensate an output brightness compared to an input brightness of the image signal. The APL adjusting unit 30 calculates an APL value of the input image signal and provides it to the light emitting number determining unit 40. The light emitting number determining unit 40 determines a light emitting number of a PDP device corresponding to the APL value and the brightness of the respective R, G and B channels.
FIG. 2A is a graph illustrating output data of a display apparatus using a conventional color temperature adjusting method. A horizontal axis represents input brightness and a vertical axis represents output brightness. The display apparatus adjusts the color temperature of an image signal inputted through the gain adjusting units 11, 12 and 13. Specifically, after determining the ratio of the respective R, G and B channels with respect to a target color temperature, the gain adjusting units 11, 12 and 13 multiplies the R, G, and B brightness values by color temperature coefficients wr, wg and wb, respectively.
However, such a conventional display apparatus has a problem that the color temperature may be distortedly expressed due to a quantization error produced when the color temperature is adjusted. In the display apparatus like a digital television set and so on, the quantization error is likely to occur during a digitalizing process of the image signal. As illustrated in FIG. 2B, the output brightness of Yr, Yg and Yb corresponds with R, G and B respectively when the input brightness is X. However, Yg does not accord with a discrete value differently from Yr or Yb, the output brightness Yg is determined as its adjacent value Y1 or Y2. That is, in the case that the output brightness value does not accord with the digitalized value in the process of applying the color temperature to the image signal, the quantization error occurs. Such a quantization error results in deterioration in an image quality and a gray scale expression due to a distortion of the color temperature.